rj79in

I've faced the same problem so now I use the Lowepro slingbag which makes maneuvering quite easy. It has a number of pockets for me to keep the lens caps and stuff. Changing lenses is a breeze without having to deal with the backpack.

I make sure that before every trip to the field, I clean the insides of the bag using the vacuum cleaner to ensure that there is no dust inside the bag. From there its pretty easy, unscrew the lens cap on the incoming lens while lens is still in the bag, remove lens from camera and put it in the bag without worrying about the lens cap. Put on the incoming lens immediately and put on the lens-cap on the outgoing lens last.

Mind you the slingbag has its own shortcomings w.r.t. space and can be used for max upto 3 lenses - including one mounted on the camera

Lots of great pointers here. I shoot a lot of outdoor editorial in varying conditions so I'll add my two cents:

I try to minimize the amount of time my sensor/mirror is exposed by prepping everything else first, i.e. lens caps, rear caps.

Use your strap and orient the camera facing down whenever you switch. Dust and debris can still float up into the body, but if it's facing down you eliminate straight on debris carried by wind, hair and sweat from your own body, exhaust grime carried by winds, etc.

Don't remove the first lens until you have the second lens ready to hot-swap with the rear cap off. Then just play Indiana Jones and put the new lens over the hole as soon as you remove the old lens. Once the new lens is secure, worry about getting the rear cap on the old lens, taking the front cap off the old lens, etc.

Basically just streamline your process so you don't wind up with your hands full fumbling with a lens cap while your body sits face-up in a dust storm.

Like others have said, my main objective in the field is to avoid switching lenses if at all possible by keeping a short and a telephoto body on hand. I don't have a lot of gear but I will just use a rebel for telephoto if I'm running short. I'd rather focus+recompose and eschew the framerate etc than mess with lenses in a chaotic situation and potentially be out a few grand for repairs.

I mostly use primes so I do the lens shuffle all the time.My second set of hands is the protective pouch that came with my RRS ballhead. I usually have a Think Tank pouch mounted outside my rucksack, so the drill goes something like this1. Put the new lens in the tripod pouch2. Remove the rear lens cap from my pocket3. Remove the lens, cap it's rear surface and drop in in the TT pocket4. Remove the rear cap from the new lense, install it and drop the rear cap in my pocket.

I chose pockets that are big enough so that the lens hoods stay on facing the direction they are used in. The lens goes in front element first but the hood prevents any chance of damage to the front element.

Once everything's settled, I may remove the rear cap from the old lens and give it a blast with a rocket blower - this depends on conditions.

When it's very dusty, you can pretty much do the job inside a plastic bag but it's easier if you sit down. If it's raining, I don't change lenses unless I can get shelter and dry the camera and lens before removing the lens.

It's important to remember, your sensor probably had scmuck on it when you purchased it. Even if you never change lenses it will add more scmuck over time. You lenses are not air tight, and neither is the camera. The lenses grow and shrink as they focus, much more as they zoom. This sucks more air in and out, brining in fresh air and squirting it around in front of the sensor. As the mechanical parts of the shutter rub against each other, they shed little pieces and create tier own scmuck.

Body facing up with lens on it set down on something. First push button and losen that lens without pulling it off yet. Hold other lens next to it facing up, remove end cap from bottom. Then fast swap and hold the one you took off the same way it came off with the open end down. Then put that end cap on that one. If you always do it that way and fast enough it's hard to get anything in there.

1. Place lens cap on2. Reverse lens hood3. Reach into bag and take out desired lens4. Remove rear element cap and place in pocket, keep the new lens in left hand.5. With right hand press button and remove old lens6. Place new lens on the camera7. With left hand now free place rear element cap on old lens8. Place old lens in bag.

I'm not very good at it myself and if I can I use a table or flat surface. If it's windy outside I'll use the bag for cover.

1. Place lens cap on2. Reverse lens hood3. Reach into bag and take out desired lens4. Remove rear element cap and place in pocket, keep the new lens in left hand.5. With right hand press button and remove old lens6. Place new lens on the camera7. With left hand now free place rear element cap on old lens8. Place old lens in bag.

I'm not very good at it myself and if I can I use a table or flat surface. If it's windy outside I'll use the bag for cover.

Better yet, choose a lens and stick to it.

This is exactly the same way I do it.

If I need both hands I will put the lens not being mounted on a camera body into my bag with the rear element down, so that it is somewhat protected from rain or dust, when the rear lens cap is off, but the front lens cap is on.